The present invention relates to automobile headlights and, more particularly, to automobile headlights which are perceived by drivers of oncoming cars as having no glare or greatly reduced glare.
The problem of automobile headlight glare is well known to everyone who has ever driven an automobile at night. The problem is particularly acute on undivided roads where only a few centimeters separate cars, and their headlights, as they pass each other heading in opposite directions.
In nighttime driving, the eyes of the driver get adjusted to the generally low level of illumination. This is typically accomplished by an automatic physiological reaction which causes the irises to open widely. In this condition, the eyes of the driver are able to perceive objects on and around the roadway which are poorly illuminated. The driver's night vision is generally not impaired by the tail lights of cars heading in the same direction since such lights are generally of relatively low intensity.
However, the situation is dramatically different whenever the subject driver encounters an approaching car, especially when the approaching car is heading parallel to the car of the subject driver on a course which will bring the two cars in close proximity of each other. As the light from the headlights of an oncoming car impinge on the eyes of the subject driver, the irises of the subject driver automatically and suddenly constrict to decrease the amount of light entering the light.
In this state, all the subject driver is able to see are the headlights. With his irises constricted, the amount of light received by the subject driver from objects other than the headlights of the oncoming car is insufficient for the subject driver to perceive them. Hence, for a few seconds starting with the near approach of the oncoming car and ending with the disappearance of the oncoming car from view as it passes alongside the subject driver, the subject driver is effectively blinded and is at risk. Of course, the driver of the oncoming car faces exactly the same problem.
But the problem is, in fact, even more severe than indicated above. The reason is physiological. The human iris is designed to constrict quickly, typically in a fraction of a second, so as to quickly and effectively protect the eye from large amounts of illumination. Unfortunately, the dilation of the human iris is a much slower process, which can take several minutes. Thus, not only is the subject driver temporarily blinded as he sees the light from the oncoming car, but the subject driver continues to suffer from impaired vision for several minutes after the oncoming car has passed as his eyes strive to dilate sufficiently for his eyes to perceive the roadway in the best way possible.
Of course, on busy roadways where oncoming cars are encountered with great frequency, the irises of the subject driver never get a chance to reach their optimal dilation and the subject driver suffers continuously from impaired vision. When being exposed to these conditions, other physical disabilities may manifest themselves, such as headaches, and the like. These could further endanger the subject driver and all those in or near the roadway.
A number of techniques and devices have been used in an effort to combat the problems. One technique which is taught in driving schools is for the subject driver to avoid staring into the headlights of the oncoming car and, instead, to turn his glance away as much as can be done with safety as the oncoming car approaches.
A well-known method which is in widespread use in the vast majority of automobiles is the possibility of switching between low beam and high beam. Under normal conditions, such as when traveling in well-lit area, at relatively low speeds on heavily travelled roads, the low beams are used. However, when driving at high speeds on highways which are inadequately illuminated low beam headlights do not provide for proper illumination of the road sufficiently far ahead of the vehicle and high beams are required.
Most headlights manufactured today feature a glass or similar front plate which is configured, typically through the use of glass of varying thickness and diffraction angles, so as to reduce glare. For example, the front plate for use in cars where driving is done on the rights are designed to diffuse light which might otherwise be directed to the left and into the eyes of the drivers of oncoming cars.
The techniques and devices mentioned above, as well as others, while somewhat effective, still leave considerable room for improvement. That improvement is still needed can be seen from the well-known fact which has been repeatedly established statistically, that per mile travelled, the rate of occurrence of traffic accidents is much greater at night than during the day. While nighttime driving is generally more hazardous due to the generally reduced visibility, there is no question that the further impairment of vision caused by the glare of oncoming cars remains a significant cause of nighttime car accidents.
There is thus a widely recognized need for a reduced-glare automobile headlight which will significantly reduce or even eliminate the problems associated with present methods and techniques.
Various attempts have been made to design a reduced-glare automobile headlight. U.S. Pat. No. 1,166,685 disclosed a complicated headlight which features a visor extending over the top portion of the headlight and which requires repeated internal reflection of the light beam prior to its emergence from the headlight. U.S. Pat. No. 1,981,328 discloses a similar system which uses a pair of curved reflecting surfaces of unusual shapes.
There have been many attempts to design headlights with a series of anti-glare opaque or reflective slats disposed across the front of the headlight so as to block the light beam and direct it at the desired angles. Illustrative of this approach are U.S. Pat. Nos. 1,115,914, 1,265,258, 1,289,814, 1,309,447, 1,333,482, 1,413,415, 1,417,128, 1,421,847, 1,442,463, 1,445,282, 1,463,024, 1,495,099, 1,500,075, 1,542,059, 1,596,831, 1,618,010, 1,631,130, 1,637,622, 1,710,187, 1,767,590, 1,797,881, 1,868,995, 2,102,928, 2,119,370, 2,478,308 and 5,077,649. The difficulty with these design is that, in each, an attempt is made to bend a light beam which is essentially horizontal in such a way that the light is directed downward to a zone in front of the vehicle. However, as is explained in more detail below, in view of today's relatively high travel speeds, the light beam must be projected to a relatively large distance ahead of the car. Doing so requires that these slats be oriented at very small angles to the horizontal. This requirement, in turn, necessitates the use of slats which are inordinately long and thus renders headlights incorporating such slats impracticable.
It would be thus desirable and highly advantageous to have an automobile headlight which includes anti-glare slats and which i of approximately the same overall size and shape as conventional headlights.